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Published online: 15 July 2009 | doi:10.1038/nchina.2009.143
Sensors: Melamine exposed
Anne Pichon
Abstract
A colorimetric sensor based on hydrogen bonding could allow on-site, real-time detection of melamine in dairy products
Original article citation
, & Hydrogen-bonding recognition-induced color change of gold nanoparticles for visual detection of melamine in raw milk and infant formula. J. Am. Chem. Soc. doi:10.1021/ja9037017 (2009).Introduction
© (2009) ACS
Melamine is a toxic, nitrogen-rich chemical normally reserved for industrial uses. However, some manufacturers have illegally added melamine to their food products to boost the nitrogen content and falsify protein measurements, resulting in poisonings that have caused renal failure and even death. Lehui Lu and co-workers at the Chinese Academy of Sciences in Changchun1 have now developed a simple colorimetric sensor that can detect even the faintest levels of melamine in aqueous solutions.
The researchers based their detection method on the well-known self-assembly of melamine and cyanuric acid derivatives through the formation of a triple hydrogen bond. Using an aqueous solution of gold nanoparticles bearing cyanuric acid derivatives, they were able to detect melamine by the change in colour of the solution — from red in the pristine state to blue in the presence of even trace amounts of melamine (see image). The formation of hydrogen-bonded complexes between one melamine molecule and up to three cyanuric acid derivatives causes aggregation of the nanoparticles, which in turn alters the optical properties of the solution.
The researchers successfully used the sensor to detect melamine at concentrations as low as 2.5 parts per billion (1,000 times lower than the maximum level permissible in Europe) within one minute. The method was also highly selective over other compounds, and worked with real milk-based products after an additional treatment step.
The authors of this work are from:
State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China.
Reference
- Ai, K., Liu, Y. & Lu, L. Hydrogen-bonding recognition-induced color change of gold nanoparticles for visual detection of melamine in raw milk and infant formula. J. Am. Chem. Soc. doi:10.1021/ja9037017 (2009). | Article |
